U.S. patent application number 13/684617 was filed with the patent office on 2014-05-29 for method for bias member charging a photoreceptor.
This patent application is currently assigned to Xerox Corporation. The applicant listed for this patent is XEROX CORPORATION. Invention is credited to Nan-Xing Hu, Johann Junginger, Gaetano J Lavigne, Yu Liu, Gregory Mcguire, Vladislav Skorokhod.
Application Number | 20140147163 13/684617 |
Document ID | / |
Family ID | 50773419 |
Filed Date | 2014-05-29 |
United States Patent
Application |
20140147163 |
Kind Code |
A1 |
Liu; Yu ; et al. |
May 29, 2014 |
METHOD FOR BIAS MEMBER CHARGING A PHOTORECEPTOR
Abstract
A bias charge member is pulsed into contact with a photoreceptor
at high frequency as a mean to reduce contamination and wearing on
both the bias charge member and photoreceptor.
Inventors: |
Liu; Yu; (Mississauga,
CA) ; Junginger; Johann; (Toronto, CA) ;
Lavigne; Gaetano J; (Burlington, CA) ; Mcguire;
Gregory; (Oakville, CA) ; Skorokhod; Vladislav;
(Mississiauga, CA) ; Hu; Nan-Xing; (Oakville,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
XEROX CORPORATION |
Norwalk |
CT |
US |
|
|
Assignee: |
Xerox Corporation
Norwalk
CT
|
Family ID: |
50773419 |
Appl. No.: |
13/684617 |
Filed: |
November 26, 2012 |
Current U.S.
Class: |
399/98 |
Current CPC
Class: |
G03G 15/0225 20130101;
G03G 15/0258 20130101; G03G 15/0233 20130101; G03G 13/025 20130101;
G03G 15/0216 20130101 |
Class at
Publication: |
399/98 |
International
Class: |
G03G 15/02 20060101
G03G015/02; G03G 13/02 20060101 G03G013/02 |
Claims
1. A method for reducing wear and contamination of a bias charging
member and a surface portion of a photoreceptor, comprising:
providing a photoreceptor; providing a bias charging member for
charging said photoreceptor; pulsing said bias charging member into
and out of contact with a surface portion of said photoreceptor to
thereby minimize power consumption, toner contamination, and wear
rate on both said surface portion of said photoreceptor and a
surface portion of said bias charging member.
2. The method of claim 1, wherein said pulsing of said bias
charging member into and out of contact with said surface portion
of said photoreceptor is accomplished with an actuator selected
from a group consisting of a piezoelectric transducer, electrical
motor, pneumatic actuator, hydraulic actuator, linear actuator,
combo drive, thermal bimorphs and electroactive polymers.
3. The method of claim 1, wherein said pulsing of said bias
charging member into and out of contact with said surface portion
of said photoreceptor is accomplished through vibration of said
charging member against said surface portion of said
photoreceptor.
4. The method of claim 1, wherein said pulsing of said bias
charging member is at a frequency from about 100 Hz to about 10
kHz.
5. The method of claim 1, wherein said pulsing of said bias
charging roll with a duty cycle from about 5% to 95%.
6. The method of claim 1, wherein said pulsing of said bias
charging member is at an amplitude from about 5 .mu.m to about 1000
.mu.m.
7. The method of claim 1, wherein said pulsing of said bias
charging member has a waveform selected from a group consisting of
square, sinusoid, and sawtooth.
8. The method of claim 3, wherein bias charge member is selected
from a group consisting of a roller, a brush, a pad and a
blade.
9. The method of claim 1, including lifting said bias charge member
away from said photoreceptor during idle time to prevent long-term
contact between said bias charge member and said photoreceptor.
10. The method of claim 4, including modulating said frequency when
said bias charge member is in the period of contact with said
surface portion of said photoreceptor to minimize friction between
said bias charge member and said surface portion of said
photoreceptor.
11. The method of claim 1, wherein the surface resistivity of said
bias charging member is from about 103 ohm/m to about 1013
ohm/m.
12. The method of claim 1, wherein said method for reducing wear
and contamination of a bias charging member is used in a
xerographic apparatus.
13. A bias charging unit comprising: a bias charging member with an
electrically conductive core; an outer layer axially supported on
the core; and an actuator configured to pulse said bias charging
member into and out of contact with a surface portion of a
photoreceptor to thereby minimize power consumption, toner
contamination, and wear rate on both said surface portion of said
photoreceptor and a surface portion of said bias charging
member.
14. The bias charging unit of claim 13, wherein the actuator is
selected from a group consisting of a piezoelectric transducer,
electrical motor, pneumatic actuator, hydraulic actuator, linear
actuator, combo drive, thermal bimorphs and electroactive
polymers.
15. The bias charging unit of claim 13, wherein a pulsing frequency
of said actuator is from about 100 Hz to about 10 kHz.
16. The bias charging unit of claim 13, wherein a pulsing duty
cycle of said actuator is from about 5% to about 95%.
17. The bias charging unit of claim 13, wherein a surface
resistivity of said bias charging member is from about 103 ohm/m to
about 1013 ohm/m.
18. The bias charging unit of claim 13, wherein said bias charging
member is selected from a group consisting of a roller, a brush, a
pad, and a blade.
19. An image forming apparatus comprising: an electrophotographic
imaging member having a charge retentive surface configured to
receive an electrostatic latent image; a development component to
apply a developer materials to the charge retentive surface to form
a developed image on the charge retentive surface; a transfer
component for transferring the developed image from the charge
retentive surface to a substrate; and a bias charging member, said
bias charging member comprising: an electrically conductive core;
an outer layer axially supported on the core; and an actuator
adapted to pulse the bias charging member into and out of contact
with said charge retentive surface of said electrophotographic
imaging member to thereby minimize power consumption, toner
contamination, and wear rate on both said surface portion of said
electrophotographic imaging member and a surface portion of said
bias charging member.
20. The image apparatus of claim 19, wherein the bias charging
member is vibrated from about 100 Hz to about 10 kHz.
Description
BACKGROUND
[0001] 1. Field of the Disclosure
[0002] This disclosure relates generally to a bias charge member,
and more particularly, concerns vibrating a bias charge member in a
printing apparatus.
[0003] 2. Description of Related Art
[0004] In a typical electrophotographic printing process, a
photoconductive member is charged to a substantially uniform
potential so as to sensitize the surface thereof. The charged
portion of the photoconductive member is exposed to a light image
of an original document being reproduced.
[0005] Exposure of the charged photoconductive member selectively
dissipates the charges thereon in the irradiated areas. This
records an electrostatic latent image on the photoconductive member
corresponding to the informational areas contained within the
original document. After the electrostatic latent image is recorded
on the photoconductive member, the latent image is developed by
bringing a developer material into contact therewith. Generally,
the developer material comprises toner particles adhering
triboelectrically to carrier granules. The toner particles are
attracted from the carrier granules to the latent image forming a
toner powder image on the photoconductive member. The toner powder
image is then transferred from the photoconductive member to a copy
sheet.
[0006] The toner particles are heated to permanently affix the
powder image to the copy sheet.
[0007] In printing machines such as described above, a bias charge
roller (BCR) is increasingly used as the major charging apparatus
in xerographic systems due to environment friendliness and
excellent charging performance. Most BCRs are contacting the
photoconductive member or photoreceptor, but some manufacturers use
a non-contact type BCR. A contact BCR provides several advantages
over traditional scorotron charging: a) uniform and stable
charging; b) reduced emissions of ozone or other corona
by-products; c) lower AC/DC voltage supply requirements; and d)
reduced service maintenance. The contact BCR will suffer from
toner/additive contamination over many printing cycles and it is
widely accepted that direct-contact BCRs increase the wear rate of
the photoconductive member, reducing overall service life of both
BCR and the photoconductive member. The non-contact BCR addresses
these issues but demands other engineering trade-offs, such as
increased knee voltage, i.e., V.sub.AC to stabilize charging with
an increased wear rate associated.
[0008] U.S. Pat. Nos. 8,126,344; 7,711,285; 7,526,243; 7,266,338;
7,079,786; 6,836,638; 6,470,161 are all directed to using
vibration-assisted cleaning systems that vibrate at a high
frequency to alleviate the adherence of particles trapped on the
cleaning surface of a photoreceptor, as well as, reduce damage on
the photoreceptor surface due to relaxation time provided by the
vibration. Examples of bias charge rollers or brushes are shown in
U.S. Pat. Nos. 7,177,572 and 6,022,660.
[0009] However, there is a continuing need for a more robustly
configured BCR.
BRIEF SUMMARY OF THE DISCLOSURE
[0010] Accordingly, in answer to this need and provided hereinafter
is a vibration-assisted bias charging unit in pulsed contact with a
photoreceptor at high frequency as a mean to reduce contamination
and wearing on both the bias charging unit and photoreceptor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Various of the above-mentioned and further features and
advantages will be apparent to those skilled in the art from the
specific apparatus and its operation or methods described in the
example(s) below, and the claims. Thus, they will be better
understood from this description of these specific embodiment(s),
including the drawing figures (which are approximately to scale)
wherein:
[0012] FIG. 1 schematically illustrates a xerographic device that
includes a bias charging member;
[0013] FIG. 2 is a schematic elevational view depicting vibration
assisted bias charging unit with pulsed contact with the
photoreceptor of the xerographic device of FIG. 1;
[0014] FIG. 3A is a chart showing a charging curve resulting from a
bias charging roll charging roll in static contact with a rotating
photoreceptor;
[0015] FIG. 3B is a chart showing visibly distorted charging curves
resulting from a bias charging roll pulsed at a driving frequency
of 0.5 Hz as related with non-uniform charging;
[0016] FIG. 3C is a chart showing a visibly distorted charging
curves resulting from a bias charging roll pulsed at a driving
frequency of 50 Hz as related with non-uniform charging;
[0017] FIG. 3D is a chart showing results of a bias charging roll
pulsed at a driving frequency of 200 Hz and an appearance of
uniform charging;
[0018] FIG. 3E is a chart showing a photoreceptor surface that is
stably charged the same as the in-contact mode shown in FIG. 3A
resulting from a bias charging roll pulsed at a driving frequency
of 1500 Hz; and
[0019] FIG. 4 is a chart showing knee curves of a contact bias
charge roll in comparison with a vibration-assisted bias charge
roll.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] While the present disclosure will hereinafter be described
in connection with a preferred embodiment, it will be understood
that it is not intended to limit the disclosure to that embodiment.
On the contrary, it is intended to cover all alternatives,
modifications and equivalents as may be included within the spirit
and scope of the invention as defined by the appended claims.
[0021] For a general understanding of the features of the present
disclosure, reference is made to the drawings. In the drawings,
like reference numerals have been used throughout to designate
identical elements.
[0022] Referring to the FIG. 1 printer 10, as in other xerographic
machines, and as is well known, an electronic document or an
electronic or optical image of an original document or set of
documents to be reproduced may be projected or scanned onto a
charged surface 12 of a photoreceptor drum 10 to form an
electrostatic latent image, although photoreceptors in the form of
a belt are also known, and may be substituted therefor. The drum
includes a photoconductive substrate deposited on a conductive
substrate and moves in the direction of arrow 16 to advance
successive portions thereof sequentially through the various
processing stations disposed about the path of movement thereof.
Motor 24 rotates roll 22 to advance the drum in the direction of
arrow 16. Drum 10 is coupled to motor 24 by suitable means such as
a drive.
[0023] Initially, successive portions of the drum pass through
charging station A. At charging station A, a corona generating
device, in the form of a bias charging roller which is indicated
generally by the reference numeral 26 connected to a high voltage
power supply 28, charges the drum 10 to a selectively high uniform
electrical potential, preferably negative.
[0024] In a digital printing machine as shown in FIG. 1, the drum
10 passes through imaging station B where a ROS (Raster Output
Scanner) 36 may lay out the image in a series of horizontal scan
line with each line having a specific number of pixel per inch. The
ROS 36 may include a laser (not shown) having a rotating polygon
mirror block associated therewith. The ROS 36 exposes the
photoconductive surface 12 of the drum 10.
[0025] It should be appreciated that the printing machine may
alternatively be a light lens copier. In a light lens copier, a
document to be reproduced is placed on a platen, located at the
imaging station where it is illuminated in known manner by a light
source, such as, a tungsten halogen lamp. The document thus exposed
is imaged onto the drum by a system of mirrors. The optical image
selectively discharges the surface of the drum in an image
configuration whereby an electrostatic latent image of the original
document is recorded on the drum at the imaging station.
[0026] At development station C, a development system or unit,
indicated by the reference numeral 34, advances developed materials
into contact with the electrostatic latent images. Preferably, the
developer unit includes a developer roller mounted in a housing.
Thus, developer unit 34 contains a developer roller 40. The roller
40 advances toner particles 45 into contact with the latent image.
Appropriate developer biasing may be accomplished via power supply
42, electrically connected to developer unit 34.
[0027] The developer unit 34 develops the charged image areas of
the photoconductive surface 12 of drum 10. This development unit
contains magnetic black toner particles 45, for example, which are
charged by an electrostatic field existing between the
photoconductive surface and the electrically biased developer roll
in the developer unit. Power supply 42 electrically bases the
magnetic roll 40.
[0028] A sheet of support material (image receiving member) 54 is
moved into contact with the toner image at transfer station D. The
sheet of support material is advanced to transfer station D by a
suitable sheet feeding apparatus, not shown. Preferably, the sheet
feeding apparatus includes a feed roll contacting the upper sheet
of a stack of copy sheets. Feed roll rotate so as to advance the
uppermost sheet from the stack into a chute which directs the
advancing sheet of support material into contact with the
photoconductive surface of drum 10 in a time sequence so that the
toner powder image developed thereon contacts the advancing sheet
of support material at transfer station D.
[0029] Transfer station D includes a corona generating device 58 in
the form of a bias transfer roll, which applies ions of a suitable
polarity onto the backside of sheet 54. This attracts the toner
powder image from the drum 12 to sheet 54, i.e., it establishes a
directional force field capable of attracting toner particles from
the photoconductive surface 12 to support material 54. After
transfer, the sheet continues to move, in the direction of arrow
62, onto a conveyor (not shown) which advances the sheet to fusing
station E.
[0030] Fusing station E includes a fuse assembly, indicated
generally by the reference numeral 64, which permanently affixes
the transferred powder image to sheet 54. Preferably, fuser
assembly 64 comprises a heated fuser roll 66 and a pressure roller
68. Sheet 54 passes between fuser roller 66 and pressure roller 68
with the toner powder image contacting fuser roller 66. In this
manner, the toner powder image is permanently affixed to sheet 54.
After fusing, a chute 70 guides the advancing sheet 54 to a catch
tray 72 for subsequent removal from the printing machine by the
operator. It will also be understood that other post-fusing
operations can be included, for example, stapling, binding,
inverting and returning the sheet for duplexing and the like.
[0031] After the sheet of support material is separated from the
photoconductive surface 12, the residual toner particles carried by
image and non-image areas on the photoconductive surface are
removed at cleaning station F. The vacuum assisted, electrostatic,
brush cleaner unit 74 is disposed at the cleaning station F to
remove any residual toner remaining on the surface of the drum.
[0032] It is believed that the foregoing description is sufficient
for purposes of the present application to illustrate the general
operation of an electrophotographic printing machine incorporating
the vibrating-assisted bias charge roll of the present disclosure
therein.
[0033] In accordance with the present disclosure and with beginning
reference to FIG. 2, an improved bias charging unit and method for
charging a photoconductive or photoreceptive surface with reduced
impact on the photoreceptor (such as wear rate), reduced
contamination on the charging unit, and uniform charging potential
on the photoreceptor is shown. In FIG. 2, vibration-assisted bias
charging roller 26 is specially equipped with a pulsed function
which forms an intermittent contact of the charging roller 26 with
the photoconductive surface 12. Bias charge roller 26 includes an
electrically conductive core 25 and an outer layer 27 axially
supported on the core. Initially, as shown at the left side of FIG.
2, bias charge roller 26 is out of contact with photoconductive
surface 12 at a predetermined height "h" and is then pulsed
serially into contact and out of contact with photoconductive
surface 12. One actuator mechanism for pulsing the bias charge
roller 26 is a conventionally mounted piezoelectric transducer
(PZT) 30. Other actuators can also be used including, for example,
an electric motor, a pneumatic actuator, a hydraulic actuator, a
linear actuator, a combination drive, thermal bimorphs and
electroactive polymers. The pulsing of the bias charging roller had
a duty cycle from about 5% to about 95%. Since charging unit 26 is
in a vibration mode, there is little chance for toner or additives
to become trapped on its surface. Thus, both of contamination and
wear rate of the bias charge roller and photoreceptor is
reduced.
[0034] While a bias charge roller 26 is shown as an example in FIG.
1, it should be understood that other bias charge members could be
used as well including, for example, a brush, a pad, a blade,
etc.
[0035] To examine charging performance of a vibration-assisted BCR,
a half-cylindrical BCR pad was fabricated with an integrated
actuator in the form of PZT to tap the BCR pad against
photoreceptor drum with the BCR pad having a surface resistivity of
from about 103 ohm/m to about 1013 ohm/m. A high voltage power
supply (HVPS) was in connection with a metal core of the BCR pad.
The BCR pad was driven by the PZT with tunable frequency and
amplitude. Between the PZT and metal core of the BCR pad, an
insulating layer was placed to protect the PZT under high voltage
shocking. Scoping tests were done on an 84 mm UDS scanner with drum
rotation speed at 3 rps.
[0036] During testing, a driving amplitude .+-.400 pm was chosen.
This amplitude has the potential to avoid trapping of charged
toner/additives on the BCR surface. The HVPS on the BCR parameters
were set as: Vdc=-500 V, amplitude of V.sub.AC from 0 to 1.3 kV,
and a 1 kHz frequency. The frequency was tuned on the PZT to drive
the BCR at different frequencies as shown in FIGS. 3A-E. As seen in
FIG. 3A, in the contact mode, the BCR was statically in contact
with a rotating photoreceptor and stably charged the photoreceptor.
At frequencies of 0.5 Hz and 50 Hz in FIGS. 3B and 3C, there are
visibly distorted charging curves as related with non-uniform
charging. When the frequency was increased, such as 200 Hz in FIG.
3D, there is an appearance of charging uniformity. With frequencies
above that, such as, at 1500 Hz shown in FIG. 3E, the photoreceptor
surface was stably charged the same as the in-contact mode shown in
FIG. 3A. Thus, it is seen that a BCR can be pulsed at high
frequency into contact with a photoreceptor surface without
affecting charging uniformity. Further, knee curves on a contact
BCR and a vibration-assisted BCR are almost the same with similar
knee V.sub.AC, which is of importance because V.sub.AC has a
significant impact on the wear rate of both bias charge members and
photoreceptors. Pulsing of the bias charging roller can be at a
frequency of from about 50 Hz to about 10 kHz and at an amplitude
of from about 5 .mu.m to about 1000 .mu.m.
[0037] Is should now be apparent that an improved bias charging
method has been disclosed that includes moving a vibrating bias
charging member into and out of contact with a photoreceptor in
order to achieve less wear on the photoreceptor. In addition, the
bias charge member stays clean due to the vibration for a longer
time thereby avoiding charging defects that lead to Image quality
defects. Also, since the bias charge member surface is making
contact with the photoreceptor only in short pulses, there is
minimized friction force between the two solid bodies. Further, at
idle times for the bias charge member, it could be lifted away from
the photoreceptor to prevent long-term contact. With the bias
charge member being pulsed into and out of contact with the
photoreceptor the contact frequency could be modulated to relax
both the bias charge member and the photoreceptor with minimized
friction.
[0038] The claims, as originally presented and as they may be
amended, encompass variations, alternatives, modifications,
improvements, equivalents, and substantial equivalents of the
embodiments and teachings disclosed herein, including those that
are presently unforeseen or unappreciated, and that, for example,
may arise from applicants/patentees and others. Unless specifically
recited in a claim, steps or components of claims should not be
implied or imported from the specification or any other claims as
to any particular order, number, position, size, shape, angle,
color, or material.
* * * * *